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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 120 |
| 5 | 1680 |
| 6 | 30000 |
| 7 | 651840 |
| 8 | 16692480 |
| 9 | 492307200 |
| 10 | 16432899840 |
| 11 | 612414190080 |
| 12 | 25205181281280 |
| 13 | 1135434972672000 |
| 14 | 55567263749437440 |
| 15 | 2935699697464934400 |
| 16 | 166525788640142131200 |
| 17 | 10094443872515806003200 |
| 18 | 651211844046521735577600 |
| 19 | 44547029929095149430374400 |
[1,2,12,120,1680,30000,651840,16692480,492307200, 16432899840,612414190080,25205181281280, 1135434972672000,55567263749437440, 2935699697464934400,166525788640142131200, 10094443872515806003200,651211844046521735577600, 44547029929095149430374400] |